Various surgical techniques have been known since the early 80's for the treatment of articular disorders. The complete replacement of an articulation of the knee is commonly practised nowadays. Rehabilitation of operated knees has become needy and different new options have been developed.
Several exercises have been proposed in different rehabilitation programs. They all aim to recover the knee to the normal articular mobility to disappearance of pain, to functional proprioception and to normal muscular function.
Currently there are four main type of exercises to aid in the rehabilitation of the knee, namely, passive, active assisted, active and "against resistance". The condition of the patient may determine the type of exercise to be practised. Traditionally, passive movement is used to allow a gain of amplitude in the articular movement by diminishing inflammatory reactions, pain or muscular cramps. The exercises requiring active muscular movement usually follow after disappearance of the pain.
A CPM (Continuous Passive Motion) apparatus is a commonly used apparatus in knee rehabilitation. This apparatus allows execution of passive flexion and extension movement during a long period of time and without effort from the patient. CPM may be very efficient in terms of reducing pain in the knee or leg in post-surgery rehabilitation treatment, reducing hospitalization time and reducing a number of complications that may occur during the rehabilitation period. However, CPM does not replace functional activity and active movement.
Once the patient is able to execute contraction of muscles without excessive pain, which may be very soon, active assisted movement of the leg is practised. It is then possible to gain range of movement (ROM) without any motorised assistance. In our experience, simple mechanical assistance in either flexion or extension movement allows greater benefits than a motorised device. Assistive active devices are necessary when muscles are not functional enough to move the joint in the devised range.
The next step to undertake for allowing full recovery of the knee or leg, that is for allowing their proper functioning, is to execute "against resistance" exercises. Actually, this type of exercise allows restoration of proprioceptive neuromuscular facilitation. It is known that rehabilitation of a muscle and maintenance of development of the muscle tone is possible from the different reflex mechanisms generated by stretching of the muscle which results from the physical action of the muscle itself.
Different publications and patents disclose an apparatus allowing application of resistance during extension of the knee through a movement of an arc of a circle. The thigh is maintained still or partially still, whether the patient is sitting or lying down. Other apparatuses comprise a simple support for receiving a thigh and a resistance device which may be a bag of sand attached to the foot. In other instances, the resistance device may be an elastic band. In all cases, the foot usually lacks proper support and the resistance is exercised on the wrong portion of the leg, for instance, in the lower portion, i.e. the shank. All these apparatus challenge the muscles in a wrong bio-mechanical way, and may damage the knee. These old-fashioned exercises are so called "open circuit" type.
Obviously, it is important to provide an apparatus that will allow execution of the exercise without causing tension on the knee. Recent data have shown the best benefits of a new approach.